Fiber preform and method and apparatus for making same

ABSTRACT

A preform suitable for the bag molding of fiber glass articles such as tanks or the like is disclosed. The preform includes a tubular portion and an integrally formed end wall at one end. The wall of the preform consists of a mat formed by a multitude of short lengths of fibers randomly oriented in the wall and bonded by a setable resin which does not fill the voids between the fibers. The form is free of overlaps and seams. A machine and a method for forming this preform is also disclosed. The machine includes a perforated form rotated about its longitudinal axis while vacuum is applied internally. Choppers deposit short lengths of fibers on the rotating form and resin is sprayed onto the fibers as they are deposited. An oven is provided to cure the resin while the preform remains on the form. Power means are provided to remove the preform from the machine. Because the form is rotating while the cutters traverse the length to deposit the fibers, the dominant orientation of the fibers is in a spiral direction. According to a further aspect of the invention, the preform is wound with a continuous filament so that the preform will have additional reinforcing strength characteristics and so that the outside diameter of the preform will be dimensioned to fit within a tubular mold with minimum clearance.

United States Patent Wiltshire et al.

[ 1 Apr. 4, 1972 [54] FIBER PREFORM AND METHOD AND APPARATUS FOR MAKINGSAME [72] Inventors: Arthur J. Wiltshire; Henry U. Ranallo, both ofCleveland; Frank E. Czumber, Chardon, all of Ohio [73] Assignee:Structural Fibers, lnc., Chardon, Ohio [22] Filed: July 5,1968

[21] App1.No.: 742,692

[52] U.S.Cl ..l56/62.4,156/172,]56/285, 161/176, 264/91 [51] Int.Cl..B29j l/02,D21j 5/00 [58] Field ofSearch ..156/173, 171, 172, 62.4,285, 156/213, 218, 62.2; 161/176; 264/113, 90, 91

[56] References Cited UNITED STATES PATENTS 2,614,058 10/1952 Francis..156/172X 3,084,088 4/1963 Hunkeler... ....l56/285X 3,137,898 6/1964Geringer ....l56/213X 3,185,182 5/1965 Waddelletal.... ....l56/173X3,210,229 10/1965 Feine ....156/213 3,449,188 6/1969 Huff ....156/1733,193,440 7/1965 Schafer 156/285 X Primary Examiner-Carl D. QuarforthAssistant Examiner-E. E. Lehmann Att0rney--McNenny, Farrington, Peame &Gordon [57] ABSTRACT A preform suitable for the bag molding of fiberglass articles such as tanks or the like is disclosed. The preformincludes a tubular portion and an integrally formed end wall at one end.The wall of the preform consists of a mat formed by a multitude of shortlengths of fibers randomly oriented in the wall and bonded by a setableresin which does not fill the voids between the fibers. The form is freeof overlaps and seams. A machine and a method for forming this preformis also disclosed. The machine includes a perforated form rotated aboutits longitudinal axis while vacuum is applied internally. Choppersdeposit short lengths of fibers on the rotating form and resin issprayed onto the fibers as they are deposited. An oven is provided tocure the resin while the preform remains on the form. Power means areprovided to remove the preform from the machine. Because the form isrotating while the cutters traverse the length to deposit the fibers,the dominant orientation of the fibers is in a spiral direction.According to a further aspect of the invention, the preform is woundwith a continuous filament so that the preform will have additionalreinforc ing strength characteristics and so that the outside diameterof the preform will be dimensioned to fit within a tubular mold withminimum clearance.

8 Claims, 11 Drawing Figures Patented April 4, 1972 3,654,002.

3 Sheets-Sheet l BACKGROUND OF INVENTION This invention relatesgenerally to the manufacture of fiber reinforced plastic articles suchas tanks or the like and more particularly to a novel and improved fiberpreform for use in the manufacture of such articles and to a novel andimproved method and apparatus for the manufacture of such preforms.

PRIOR ART In the manufacture of fiber reinforced articles such as tanksand the like, one commonly used method employs forming one or two endpreforms and positioning them in a mold with a rolled blanket usedforforming the tank side wall. The fiber forming the preform and theblanket is then compressed by inflating a bag within the mold. A resinis then caused to flow through the fiber mat and is cured. Examples ofpatents describing this method of manufacture are the U.S. Fat. toWiltshire No. 3,138,507 andGeringer No. 3,137,898.

Since the fiber-reinforcing blanket used in such method to form thesidewalls is formed by rolling a flat sheet of fiber material, alongitudinal overlap results in a uneveness in the amount offiber-reinforcing material along the longitudinal overlapping portion ofthe blanket. Further, since the end preforms are separately formed, anoverlapping joint is required between the side wall blanket and thepreforms. Here again, an irregularity in the amount of reinforcingmaterial is present at the overlapping joints. Still further, thelapping of the joints does not provide a uniform interlocking of thefibers in the area of the lap.

SUMMARY OF INVENTION The present invention is directed to a novel andimproved preform which includes a tubular section and an integral endthereon wherein the fiber forming the preform is uniformly distributedalong the entire preform and is distributed along the wall of thepreform so the final product provides a uniform high strength withoutexcessive amounts of fiber in any location.

The fiber of the preform consists of short lengths of fiber which arerandomly oriented to provide substantial interlocking in the fibers ofthe completed article. However, the orientation of the fibers isarranged so that there are more fibers extending in a spiral patternaround the tubular section of the preform than lay in other directions.Therefore, the maximum strength of the finished article is available toresist the hoop tension when the article is subjected to internalpressure. Further, the preform includes an integrally formed end joinedto the tubular section without any lap so that the maximum amount ofstrength is achieved with a minimum of fiber material.

The invention also provides a novel and improved method and apparatusfor forming a preform for fiber reinforced articles of the typedescribed above. The apparatus for performing the method of thisinvention includes a perforated form which is rotated about itslongitudinal axis while a vacuum is applied internally. A pair ofchoppers cut fiber reinforcing material, such as glass fibers, intoshort lengths and direct the fibers toward the rotating form. The vacuumapplied to the perforated form causes the fibers to be laid up in arandom manner. However, since the form is rotating with respect to thecutters while the cutters traverse longitudinally to deposit the fibersthereon, the dominating orientation of the fibers is in the direction ofa spiral extending around the perforated form. The two cutters arearranged with one ahead of the other to sequentially deposit the fiberand insure uniformity.

A binder which is preferably a thermosetting resin is sprayed onto thefibers as they are deposited on the form. The form is provided with aperforated end wall which closes one end of the perforated form and themachine is arranged to deposit the resin and fibers uniformly around theend so the end of the preform is integrally formed with the side wallportion and the fibers are uniformly distributed along the entiresurface of the preform including the end.

The apparatus also provides an oven so that the resin of the preform canbe cured before it is removed from the machine. Still further, themachine is provided with power means to remove the preform from themachine.

OBJECTS OF INVENTION It is an important object of this invention toprovide a novel and improved preform for the use in manufacture of fiberreinforced articles such as tanks or the like wherein the fibers of thepreform are uniformly distributed along the entire wall surface thereof.

It is another important object of this invention to provide a novel andimproved method and apparatus for manufacturing a preform as set forthin the preceding object.

Further objects and advantages will appear from the followingdescription and drawings wherein:

FIG. 1 is a schematic side elevation of a machine incorporating thisinvention.

FIG. 1a is a perspective view of a preform incorporating this invention;

FIG. 2 is a schematic end view of the machine illustrated in FIG. 1;

FIG. 3 is a schematic plan view of the machine;

FIG. 4 is a perspective view of one type of perforated form which may beused on the machine illustrated in FIGS. 1 through 3;

FIG. 5 is an enlarged fragmentary section taken along 5-5 of FIG. 4illustrating a lock for the form illustrated in FIG. 4;

FIG. 6 is a perspective view of the support for the form illustrated inFIGS. 4 and 5;

FIG. 7 is a side elevation of a second type of perforated form which maybe used on the machine of FIGS. 1 through 3;

FIG. 8 is an enlarged fragmentary section taken along 8-8 of FIG. 7;

FIG. 9 is a fragmentary perspective view of one part of the formillustrated in FIG. 7; and,

FIG. 10 is a fragmentary view of a filament winding apparatus providedon the machine.

FIG. la illustrates one embodiment. of a preform 9 in accordance withthe present invention. This preform is particularly adapted for themanufacture of tanks of the type often used for water softeners or thelike. The preform includes a cylindrical wall portion 10 extending froman open end 11 to a generally spherical closed end 12. The preform wallis a loose mat consisting ofa multitude ofshort lengths offibers 13,such as glass fibers, randomly oriented in the wall forming the cylin-.

drical portion 10 and the end wall 12.. The fibers are interlocked witha setable resin such as a thermosetting polyester resin which does notfill the voids between the fibers. Therefore, the preform is relativelycompressible and voids are provided so that the preform is well adaptedfor use in the manufacture of finished articles in accordance with thegeneral method described in the patents cited above.

The illustrated preform is of the type often used in the manufacture ofa pressure vessel, and such products are subjected to substantial hooptension. Therefore, the fibers, although randomly oriented, arepreferably arranged so the dominant orientation of the fibers in aspiral direction around the preform as indicated by the arrow 14. Theend 12 of the preform is also formed by randomly oriented fibers bondedby a setable resin and has substantially the same density and thicknessas the wall portion 10.

In one embodiment of this invention, a preform is manufacv In fact thewall of the preform is substantially uniform in density and thicknessthroughout its extent.

In some instances where higher hoop strength is required, the preform iswound with continuous fiber strands as illustrated at 16. In FIG. la thewinding 16 is illustrated only at one end to demonstrate how the preformmay be wound. However, the winding can, and normally would, extend thefull length of the preform. Such a preform with peripheral winding issuitable for the manufacture of pressure vessels having higher hoopstrength requirements.

Reference-should now be made to FIGS. 1 through 3 for a clearunderstanding of a machine for manufacturing a preform of the typeillustrated in FIG. 1a. This machine includes a frame 21 which supportsspaced bearings 22 and 23 which journal a rotatable tubular formsupporting duct 24. A perforated form 26 is mounted on the end of thetubular duct 24 for rotation therewith. A drive chain 27 is connected toa sprocket 28 on the tubular duct 24 and is driven by a motor 29 toprovide the motive power for rotating the tubular duct 24. The end ofthe tubular duct 24 opposite the form 26 is connected to a non-rotatingduct 31 through a coupling 32 which provides an air-tight jointtherebetween while permitting relative rotation. The duct 31 connects toa fan 33 driven by a motor 34 so that the fan 33 applies a vacuum to theperforations of the form 26. The air from the fan is exhausted through aduct 36.

In the preferred embodiment of the machine, there are two spaced, butparallel, rotating form supporting ducts 24 which are similar to eachother and which are connected through a Y-fitting 37 (illustrated inFIG. 3) to the fan 33. A damper 38 is located in the Y to permit thevacuum produced by the fan 33 to be selectively applied to one or theother of the forms as described in more detail below.

The illustrated embodiment of the machine incorporates two similar formsand two groups of accessory equipment associated with each form.Therefore, only one form and its associated accessories will bedescribed in detail with the understanding that the description appliesequally to the other form and its associated accessories.

Mounted on a track 39 which extends above the form 26 is a carriage 41which is supported by the track 39 for traversing movement along thelength of the form 26. A motor 42 is connected through a chain 43 toprovide the power for traversing the carriage 41. Mounted on thecarriage 41 are two similar fiber choppers 44 and 46 which are spacedfrom each other in the direction ofthe length of the form 26. A singlemotor 47 is connected to drive the two choppers through suitableclutches. These choppers 44 and 46 operate to cut continuous filamentsof the fiber glass or the like into short lengths to form the separatedpieces of fiber and operate to direct the cut pieces downwardly againstthe form 26 as illustrated at 48 and 49.

Also mounted on the carriage 41 are a pair of spray nozzles 51 and 52which are supported beside the form 26 on a retractable arm 53. Thesenozzles 51 and 52 are adapted to spray the settable resin onto theexterior of the form in the area in which the cutters 44 and 46,respectively, are depositing pieces of fiber.

Positioned beside each form 26 is a curving oven which can be closedaround the form after the fiber and resin are deposited thereon to heatthe resin and cure it before the preform is removed from the machine.The oven includes a burner box 54 mounted beside the form 26. Pivotallymounted on the burner box 54 is a lower cover 56 pivoted at 57 formovements between retracted and extended positions. The cover 56illustrated in the right side of FIG. 2 is retracted and the cover 56 asillustrated in the left side of FIG. 2 is extended. The power for movingthe covers 56 between the extended and retracted positions is suppliedby associated motors 58 connected by chains 59 to the covers 56. The topof the cover 56 is closed by a retractable top closure 61 which isslidable along the top of the burner box 54 between retracted andextended positions. Here again the closure 61 illustrated at the rightof FIG. 2 is retracted and the closure at the left is extended.Actuators 62 are provided for the retraction and extension of theassociated closures 61. When the lower cover 56 and the top closure 61are extended as illustrated on the left, the associated form 26 iscompletely enclosed so that the hot air from the burner box 54 heats thepreform to cure the resin. After the curing cycle is completed, thecover 56 and the closure 61 are retracted to provide access to thepreform. The retractable arm 53 which supports the nozzles 51 and 52 ismoved to a horizontal position as illustrated in the left of FIG. 2during curing so that the nozzles are clear of the curing ovenstructure.

FIGS. 4 through 6 disclose one preferred embodiment of a form structureand the structure of the support for the form. Mounted on the machine isa form support structure 65 illustrated in FIG. 6. This supportstructure includes a face plate 66 which is adapted to be bolted to amating face plate 67 (illustrated in FIG. I). Extending from the faceplate 66 are four symmetrically positioned support rods 68 which areanchored at one end on a flange 69 on the face plate 66 and are anchoredat their opposite end on an end form element 71. Intermediate support isprovided by a ring 70.

The end form element 71 is provided with a generally sphericalperforated end wall 72 and axially extending flanges 73. A cylindricalremovable element 74 (illustrated in FIG. 4) is proportioned to fit overthe rods 68 to cooperate with the end element 71 to form the completeform 26. The cylindrical element 74 is formed with lateral projections76 at one end and is proportioned so that when the cylindrical element74 is properly positioned on the support 65, the lateral projections 76are positioned adjacent to one side of a push-off ring 77 mounted on themachine. The push-off ring 77 (illustrated in FIGS. 1 and 2) is axiallymovable along the form support by actuators 78 to cause the cylindricalelement 74, along with the preform, to be stripped off the form support.The open end of the cylindrical element 74 opposite the projection 76 ispro portioned to overlap the flange section 73 a slight amount so thatthe form is continuous when assembled. Preferably the end element 71 andthe cylindrical element 74 are formed of sheet stock which is providedwith perforations along the entire surface.

After the cylindrical element 74 and the preform formed therearound isstripped off of the support illustrated in FIG. 6, the preform can becollapsed by releasing lock pins 80 to collapse the form. As illustratedin FIG. 5, the lock pins 80 are carried by one longitudinal edge 79 andare positioned to project through mating openings 81 along the oppositelongitu dinal edge to maintain the form to the extended position. Whencollapse of the form is required, the edge 79 is pulled inwardlyreleasing the lock pins 80 and allowing the form to collapse inwardly asillustrated in phantom in FIG. 5. The preform can then be removed fromthe cylindrical element 74 and the element can be reused to form asubsequent preform.

The machine is preferably controlled by a suitable automated controlsystem to automatically operate through a predetermined cycle. Suitablelimit switches and control circuits are provided for this automatedoperation. However, the circuitry is not illustrated since personsskilled in the art can easily provide suitable circuits to produce thedesired operational cycle.

At the beginning of a cycle a cylindrical element 74 is positioned onthe form support and the damper 38 is shifted to connect the inlet ofthe fan 33 to the form. This applies a vacuum to the perforations of theform. The motor 29 is energized to cause rotation of the form. Thecarriage 41 is traversed to the left as viewed in FIG. 1 until thecutter 46 is adjacent to the end of the form 26 remote from the closedend.

The operation of the cutter 46 is initiated to cause fibers to feed froma spool 82 (illustrated in FIG. 2) to the cutter where the continuousstrands are chopped into short lengths of fiber. The cutter thenoperates to direct the short lengths of fiber onto the form where thevacuum causes the fibers to collect.

The operation of the nozzle 52 is then initiated to cause the resin tobe sprayed onto the fibers as they are deposited on the form.

The deposit of fibers at the open end of the form occurs for apredetermined length of time before the traversing motor 42 is startedto cause the carriage to traverse toward the closed end of the form.This insures that a sufficient layer of fibers will be deposited at theopen end of the form. The motor 42 is then energized to cause thecarriage to traverse to the right as viewed in FIG. 1 toward the closedend of the form. When the carriage is traversed along the form for asufficient distance to position the cutter 44 at the open end of theform, this cutter is also started by engaging its clutch and theoperation of the nozzle 51 is initiated. The carriage 41 continues totraverse along the form depositing the fibers thereon toward the closedend formed by the end element 71. Since the cutter 44 traverses behindthe cutter 46, two separate applications of fiber and resin is suppliedto the form to insure that a uniform thickness will be produced in thewall ofa preform.

When the carriage reaches the phantom position of FIG. 1, the cutter 46is directing fibers down along the end surface 72 of the end element 71.Because the fibers along the cylindrical portion of the form partiallyclose the adjacent perforations, there is a tendency for the vacuum tobuild up at the end by the time it is coated with fibers. This assistsintending to cause the fibers to be properly positioned around the endto completely close the end and form a uniform wall thickness thereon.

When the cutter 46 reaches the phantom position, the operation of thecutter 46 and its associated nozzle 52 is terminated, but traversing iscontinued until the cutter 44 reaches the end of the form. At this timethe operation of the cutter 44 and the associated nozzle 51 isautomatically terminated, completing the deposit of fiber and resin onthe form.

The carriage 41 can then be traversed back to its initial position andthe nozzles are moved up out of the way by movement of the retractionarm 53 to the horizontal position. The actuator 62 and the motor 58 arethen operated to extend the lower cover 56 and the top closure 61 sothat the form with the preform thereon is enclosed for curing. Theburners, which may be of any suitable type such as gas burners, thensupply heat to cure the resin. After the resin is cured, the top 61 andthe cover 56 are retracted clear of the form and preform. The actuators78 are then operated to strip the cylindrical element 74 off of the formsupport. This stripping action causes the fibers at the end to move freeof the end element 71 since the resin is already cured and the preformis sufficiently rigid to permit this action. The cylindrical element isthen collapsed and the preform is removed, completing the cycle ofoperation.

It should be appreciated that the form 26 may be traversed with only onecutter and its associated nozzle in operation and then traversed in theopposite direction by the other cutter and its associated nozzle whilethe form 26 is rotated in the same direction. This will produce apreform wherein the orientation of the fibers is random but with morefibers extending in a helical pattern. Such a helical pattern may alsobe produced by traversing the form 26 in one direction with a singlecutter and associated nozzle, reversing the rotation of the form 26while again traversing the form in the same direction with the othercutter and its associated nozzle operating.

By providing two forms on the machine and twogroups of accessories, themachine can be cycledso that the curing of one preform on one form isoccurring while the fiber and resin are applied to the other form. Inthis way, the output of the machine can be relatively continuous eventhough only one fan is utilized to produce the vacuum in the forms.

FIGS. 7 through 9 illustrate a second embodiment of a form which may beused with this machine. This form again includes a mounting flange 101which can be secured to the flange 67 of the rotating duct 24. The formincludes two parts 102 and 103 which cooperate, when the two parts arein the position illustrated in FIG. 7, to produce the cylindricalportion and the generally spherical end wall portion of the device. Theupper part 102 is rigidly mounted on the mounting flange 101 and thelower part is supported by the upper part by inclined connectors (bestillustrated in FIGS. 8 and 9). These connectors include an upper plate104 and a lower plate 105. The upper plates are secured to the upperpart 102 at spaced locations and the lower plates 105 are secured to thelower part. 103 at similar spaced locations. Mounted on the upper plates104 are headed fasteners 106.which extend through slots 107 in the lowerplates 105 and are provided with heads 108 which hold the platestogether. Therefore, the two parts 102 and 103 are held together alongan inclined plane, but are axially movable relative to eachother. Thelower part 103 is provided with peripherally spaced lateral projections109 which are engaged by the stripper ring 77 when the stripper ring isextended.

With this embodiment, extension of the actuator 78 causes the lower part103 to move along the upper part and causes the preform to be carriedalong the upper part 102 to a location where thecombined peripheralextent of the upper and lower parts is smaller, and the preform may beremoved without completely removing the lower part 103 from the machine.

If the preform is to be wound with a continuous filament, a filamentmetering device 111 is provided. The device 111 has a filament meteringroll 112 which is driven on a lzl ratio with the duct 24 and the form 26by a suitable drive chain 113 and bya sprocket (not shown) provided on;the duct 24. The drive chain 113 cooperates with a sprocket 114 whichdrives a splined shaft 115. The metering roll 112 is slidably mounted onand is driven by the splined shaft 115. A pinch roll 116 cooperates withthe metering roll 112 and the rolls 116 and 112 are mounted within ahousing 117. The housing 117 is driven by a lead screw 118 so that therolls 112 and 116 traverse the extent of the cylindrical side wall ofthe preform.

The splined shaft extends through the housing 117 by means of suitablebearings which permit the shaft 115 to rotate relative to the housing117 but permit the housing 117 to be driven relative to the axis of theshaft 115. Suitable spacers are provided between the metering roll 112and the housing 117 so that the roll 112 does not rub on the housing.The lead screw 118 is powered by a reversing motor 119.

With a continuous filament trained between the rolls I12 and 116, andattached to the preform, the rate of traverse of the filament isadjusted with respect to the rotational speed of the preform to providethe desired orientation and density of the peripheral windings on thepreform. After one pass with the continuous filament, the motor 119 maybe reversed to provide another winding on the preform at a predeterminedangle with respect to the first winding. The diameter of the roll 112 isslightly smaller than the inside diameter of the hollow mold into whichthe preform is to be inserted so that the wound outside diameter of thepreform will just clear the inside diameter of the hollow mold and fitsnugly therein. It should be appreciated that if substantial clearancewere provided between the preform and inner surface of the mold, themolded article would have an undesirable resin rich outer surface whichwould be subject to crazing or cracking.

With the machine and method incorporating this invention, a uniformpreform may be produced. If a thicker wall is desired, the traversingspeed of the carriage 41 can be reduced or the speed of the choppers 44and 46 can be increased. Similarly, the amount of resin deposited can beregulated by adjusting the flow through the nozzles 51 and 52. It hasbeen found that preforms incorporating this invention provide a moreuniform, higher strength finished article with a minimum total fibercontent, since overlaps at the closed end of the preform and lengthwiseof the preform are eliminated.

Although a preferred embodiment of this invention is illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted to without departing from the scope of the inventiondisclosed and claimed herein.

We claim:

l. A method of manufacturing a preform for fiber reinforced plasticarticles comprising rotating about its longitudinal axis, an elongatedcylindrical hollow tube having a closed end and having perforations inits entire outer surface including said end, applying vacuum to theinside of said form to draw air through said perforations, and, whilesaid vacuum is applied, directing a large number of randomly orientedshort pieces of fiber against the outside surface of said rotating formby uniformly traversing the length of said form with a source of fibersto produce a uniform mat on the exterior surface thereof, stopping thetraverse of said source adjacent said closed end and depositing fiberson said end, spraying said fibers with a thermosetting resin to bindsaid fibers together to form a preform without filling the voids betweensaid fibers, and curing said resin while said preform remains on saidform.

2. A method of manufacturing a preform as set forth in claim 1 whereinsaid fibers are deposited on said rotating form by traversing the lengthof said form more than once with a source of fibers to insure an evendistribution of fibers on said form.

3. A method of manufacturing a preform as set forth in claim 2 whereinthe form is traversed along its length in one direction and in anopposite direction with said source of fibers while said form is rotatedin the same direction.

4. A method of manufacturing a preform as set forth in claim 2 whereinsaid fibers are deposited on said rotating form my traversing the lengthof said form in one direction while said form is rotated in a firstdirection and rotating said form in a second direction while againtraversing the length of said form with said source of fibers in saidone direction.

5. A method of manufacturing a preform as set forth in claim 1 whereinat least two sources of fibers are provided and both sources traversesaid form in the same direction.

6. A method of forming a preform as set forth in claim 5 wherein longstrands of fibers are cut into short pieces by said source.

7. A method of forming a preform as set forth in claim 1 wherein saidform is subsequently collapsed to permit removal of said preform.

8. A method of forming a preform as set forth in claim 1 includingwinding :1 continuous filament about the exterior of said preform priorto curing.

1. A method of manufacturing a preform for fiber reinforced plasticarticles comprising rotating about its longitudinal axis, an elongatedcylindrical hollow tube having a closed end and having perforations inits entire outer surface including said end, applying vacuum to theinside of said form to draw air through said perforations, and, whilesaid vacuum is applied, directing a large number of randomly orientedshort pieces of fiber against the outside surface of said rotating formby uniformly traversing the length of said form with a source of fibersto produce a uniform mat on the exterior surface thereof, stopping thetraverse of said source adjacent said closed end and depositing fiberson said end, spraying said fibers with a thermosetting resin to bindsaid fibers together to form a preform without filling the voids betweensaid fibers, and curing said resin while said preform remains on saidform. Pg,21
 2. A method of manufacturing a preform as set forth in claim1 wherein said fibers are deposited on said rotating form by traversingthe length of said form more than once with a source of fibers to insurean even distribution of fibers on said form.
 3. A method ofmanufacturing a preform as set forth in claim 2 wherein the form istraversed along its length in one direction and in an opposite directionwith said source of fibers while said form is rotated in the samedirection.
 4. A method of manufacturing a preform as set forth in claim2 wherein said fibers are deposited on said rotating form my traversingthe length of said form in one direction while said form is rotated in afirst direction and rotating said form in a second direction while againtraversing the length of said form with said source of fibers in saidone direction.
 5. A method of manufacturing a preform as set forth inclaim 1 wherein at least two sources of fibers are provided and bothsources traverse said form in the same direction.
 6. A method of forminga preform as set forth in claim 5 wherein long strands of fibers are cutinto short pieces by said source.
 7. A method of forming a preform asset forth in claim 1 wherein said form is subsequently collapsed topermit removal of said preform.
 8. A method of forming a preform as setforth in claim 1 including winding a continuous filament about theexterior of said preform prior to curing.